Injection molding is commonly used to form plastic articles that are relatively rigid in nature, including containers, medical devices, and so forth. For example, containers for stacks or rolls of pre-moistened wipes are generally formed by injection molding techniques. One problem associated with such containers, however, is that the molding material is often formed from a synthetic polymer (e.g., polypropylene or HDPE) that is not biodegradable or renewable. The use of biodegradable polymers in an injection molded part is problematic due to the difficulty involved with thermally processing such polymers. Polylactic acid, for example, tends to undergo a much greater degree of expansion during molding than other types of polymers (e.g., polyolefins). Therefore, when it is desired to form a molded part from polylactic acid, a new molding apparatus (e.g., die) is required, which is extremely costly. Furthermore, polylactic acid also has a relatively high glass transition temperature and demonstrates a high stiffness and modulus, while having a relatively low ductility. This significantly limits the use of such polymers in injection molded parts, where a good balance between material stiffness and strength is required.
As such, a need currently exists for a polylactic acid composition that is capable of exhibiting good mechanical properties so that it can be readily employed in injection molded parts.